The invention relates to a safety belt system having a tension-relieving mechanism and more specifically to a belt system with a tension-relieving mechanism continuously applying a nominal load on the wearer in the tension-relieving mode.
Tension-relieving mechanisms are frequently placed into the tensionless or comfort mode by protracting the latched or secured seat belt and releasing the belt to allow a slight belt-rewind movement. This sequence of actions in a known tension-relieving system moves an internal locking pawl to engage a ratchet wheel fixed to the reel shaft, which prevents continued rewinding of the belt onto the reel under the force of the reel biasing means. Thus, the force of the rewind spring acting to rewind the shoulder belt is relieved from a vehicle occupant's shoulder. Such devices are shown in U.S. Pat. Nos. 3,851,836; 3,869,098; and, 3,834,646. The conventional tensionless mechanisms frequently have a memory system, which allows the occupant to move slightly forward a short distance in his seat to extract one or two inches of seat belt from the retractor without canceling the tensionless mode. Thus, if the occupant moves forward in his seat and then returns to the original tensionless position, the tension-relieving pawl again engages a ratchet wheel to relieve the belt tension from the rewind spring. Protracting the seat belt more than the memory distance shifts the tension-relieving mechanism to its disengaged or release position, which allows the rewind spring to freely act on the reel to tightly rewind the belt against the occupant. A door release operator may similarly disable the tension-relieving mechanism and allow the retractor spring to rewind the seat belt toward its fully wound position on the seat belt reel. This assures that seat belts are fully wound upon an occupant's leaving the vehicle.
Other actuator systems for tension-relieving may be set into their tensionless state by an overt act of the occupant, such as moving a switch to close a circuit and energize a solenoid. This solenoid shifts a pawl into locking engagement with a ratchet wheel to immediately place the tensionless system into its tension-relieving state, irrespective of occupant location. Thus, if one or more inches of slack are in the belt when the actuator means is engaged, the amount of belt slack is not reduced even through the occupant may move back in the seat. Such a tensionless system was disclosed in U.S. Pat. No. 4,585,185, and it is released or disengaged by a subsequent operation of a switch means. Manipulation of the belt beyond the memory distance will not cause automatic rewinding of the belt in this system, as the solenoid has shifted the tension-relieving pawl into its engaging position and an electrical switch operation is required to switch the solenoid to another state.
The present invention provides a tensionless system for a seat belt retractor assembly and more specifically provides a tensionless system which reduces the overall retractive load upon the vehicle occupant restrained by the seat belt to less than the total retractive force. However, the small retractive load at the tension-relieving mode, which is provided at assembly, maintains the belt firmly but unobtrusively against the occupant. The tensionless or tension-relieving system is not immediately set into the tensionless mode by a belt movement, but is generally set into the tensionless mode by protracting the belt a small supplemental distance from the housing after belt securement and initial retraction against the body of the vehicle occupant. The tension-relieving mode is actuable by either the conscious movement of the occupant to extract or protract the belt the fixed distance, or alternatively, an inadvertent forward movement of the passenger to protract the belt the required tensionless-mode-setting distance. The tension-relieving mode reduces the retractive load on the belt, and thus the belt tensile load felt by the occupant, to a level that secures the occupant with the belt against his body but prevents any looseness or slack in the belt while in the tensionless state. The tensionless mechanism further incorporates a comfort system with a memory for recovery of the tensionless mode and means for canceling the tensionless mode, which may be actuated by a remote operator or by belt disengagement.